Macro and microvascular diseases are the principal causes of morbidity and mortality in patients with type 1 and type 2 diabetes. Endothelial dysfunction, as evidenced by the increased release of free radicals, increases adhesion molecules and apoptosis. Previous work by us and others has shown that a decrease in HO-1 gene expression enhances apoptosis and vascular injury which can be prevented by pharmacological mediated upregulation of HO-1. Our preliminary results indicate that upregulation of HO-1 prevents endothelial apoptosis by decreasing cellular heme content, increasing CO and bilirubin levels and decreasing EC-SOD and DNA degradation. The goal of this proposal is to elucidate the mechanism by which HO-1 prevents diabetes-mediated endothelial dysfunction and to explore the use of genetic and/or pharmacological approaches to achieve long-term vascular protection. Our hypothesis is that HO-1 gene transfer will provide powerful vascular protection by increasing heme degradation and subsequently increasing CO and bilirubin synthesis. The increased levels of CO and bilirubin will result in an increase in EC-SOD, and eNOS, a decrease in O2- and improved vascular response. In addition, increase in mitochondrial HO-1 levels will increase mitochondrial transport carrier, decrease mitochondrial ROS and prevent release of cytochrome c and activation of caspase 9. We plan to test this hypothesis using genetic probes (retroviral LXSN lentiviral, and adenoviral) and in genetically spontaneously diabetic mice, (NOD) mice. We will use the loss-of-function HO-2 (-/-) and gain-of-function, HO-1 and HO-2 gene transfer to HO-2 (-/-) to decipher the role of each gene in vascular protection. The following specific aims will test the hypothesis. (1)To determine whether genetic intervention, using retroviral vectors, to selectively increases HO-1 provides vascular protection in diabetic rats and NOD mice, and whether this effect is due to CO, bilirubin or both. We will examine the effect HO-1 derived CO and bilirubin on EC-SOD, eNOS and O2- levels. (2) HO-2 (-/-) and NOD mice will be used to test the hypothesis that HO-1 gene transfer can provide vascular protection and that CO, bilirubin or both are obligatory for the vascular protection via increase in EC-SOD, eNOS, decrease in O2- and iNOS. (3)To determine the mechanism whereby HO-1 gene expression (CO and bilirubin) act on the extrinsic and intrinsic pathway of pro-apoptosis and anti-apoptotic proteins. This will examine the role of CO and bilirubin produced by HO-1 in both the mitochondria and cytoplasm. (4) To evaluate whether lentiviral vectors targeting endothelial cells using cell specific promoter (VE-CAD) to overexpress HO-1 gene is sufficient to offset diabetes-induced vascular injury. This proposal is novel in its approach. It will allow for the first time, an in-depth analysis of the function of HO-1 in vascular protection and for the development of innovative gene-targeting therapies for the treatment of type I diabetes.